Loudspeaker

ABSTRACT

Stable, distortion free response and a substantially flat output curve is obtained from a loudspeaker in which the diaphragm suspension periphery extends forward of the diaphragm and seats on a resilient humidity non-sensitive gasket and is secured by clamps which bear superjacently on the gasket sealably compressing it without distorting the frame.

United States Patent Rollins 14 1 July 1,1975

181/31 R 181/172 Shiga et a1. 181/32 R FOREIGN PATENTS OR APPLICATIONS [541 LOUDSPEAKER 3,137,836 6/1964 Glover 3,645,356 2 1972 S t [76] Inventor: William L. Rollins, Monroe, W15. 3 717 218 2x973 0 mm:

390,109 3/1933 United Kingdom..i.i.......... 181/31 R [22] Filed: July 2, 1973 [21] Appl. No.: 375,729

[51] Int. Cl. Gl0k 13/00; H04r 7/00 [58] Field of SearchMHm. 181/32 R. 31 B, 24, 172, 181/171 [56] References Cited UNITED STATES PATENTS 3 Claims, 3 Drawing Figures nonsensitive gasket and is secured by clamps which bear superjacently on the gasket sealably compressing it without distorting the frame.

1.876306 9/1932 2,123,442 7/1938 Stone......4

2,640,556 6/1953 Brennanmm 3,095,941 7/1963 Hassan....4.t..,....t...............

PATENTEDJUL' 1 ms SHEET Figure I LOUDSPEAKER BACKGROUND OF THE INVENTION A conventional loudspeaker may comprise a dishshaped frame or basket" with a permanent magnet centrally fixed at the rear and a frontal diaphragm fiexi bly suspended by a collar or surround secured to the rim. The magnet structure is configured with an air gap in which a voice coil wound on a cylindrical support member is disposed carried by the diaphragm for free axial movement in the air gap. The voice coil, support member and diaphragm move in response to the resultant created by the interaction of the fields of the magnet and the voice coil, the input to the voice coil being amplified current received directly or recorded from a transducer. Actuation of the diaphragm generates sound waves in the surrounding air medium reproducing with amplification the acoustic input to the transducer.

The loudspeaker is usually mounted on a gasket surrounding an opening in a mounting board or baffle with the rim of the loudspeaker being secured to the baffle by screws. A fiat gasket is commonly used, frequently comprising cellulosic material, with the screws being arranged encircling the gasket. When mounted in this manner, the frame of the loudspeaker is subject to distortion by the force of the screws and the gasket acting thereon in offset relation, the distorting effect being aggravated if the gasket comprises humidity sensitive material such as cellulose which will shrink and swell with changes in ambient humidity, warping the frame in a variable manner and rendering component alignment unstable.

Acoustic response of a loudspeaker is greatest for given input power at the resonant frequency of the speaker and lessens towards the extremes of the sound spectrum. To compensate for non-linear, frequency dependent characteristic of acoustic response to input power, multiple speaker enclosures embodying speakcrs of different resonant frequencies are commonly provided to more nearly approximate desirable linear reponse characteristic.

SUMMARY OF THE INVENTION The loudspeakers of this invention exhibit excellent mechanical stability and near linear characteristic of acoustic response to input power substantially through out the audible frequency range, typically to within four to five decibels of constancy for a moderate size speaker from below 70 cycles per second (cps) upward through 20,000 cps. Stability and constancy of reponse that are exhibited are achieved in part by the frame of the speaker and the outer peripheral portion of the diaphragm suspension collar being configured forwardly extending to a plane substantially, at least, coincident with that of the most forwardly biasable position of the diaphragm, and being seated on a tightly sealing, humidity nonsensitive, resilient gasket, and being secured by clamps which bear upon the gasket and rim assembly superjacently without offset relation and without imparting stress which would disrupt alignment be tween the magnet and voice coil or other component parts.

The configuration of the juncture of the baffle opening with the deep wall of the surround is almost smooth and continuous and may combine synergistically with other recognized factors to provide the demonstrable superiority of the speakers of this invention in con stancy of ratio of acoustic output to input power virtually throughout the usable frequency range making possible broad spectrum, high fidelity sound reproduction utilizing but one speaker.

DESCRIPTION OF THE INVENTION FIG. 1 is a partial cross-sectional side elevation of a loudspeaker and fastening means of this invention shown in juxtaposition with a mounting board;

FIG. 2 is a partial cutaway rear elevation of the article of FIG. 1 with the loudspeaker disposed similarly facing, for mounting on the opposite side of the mount ing board;

FIG. 3 is a side elevation in partial cross-section of a peripheral portion of another embodiment of the invention.

In FIG. 1 loudspeaker 9 is shown comprising a dish configured metal structural member, hereinafter called basket ll, juxtaposed within opening 13 of mounting board 12. Lip 16 of basket 11 is disposed for seating on mounting board 12 peripherally of opening 13. Truncated conical diaphragm 14 is disposed within the confines of basket ll with its outer periphery bonded to a pliant annular collar, hereinafter called surround l7, and its inner periphery bonded to the end of voice coil support member 15. Surround I7 is configured with its outer periphery overlaying the front of lip 16 to which it is adhesively secured, and with its mid-portion con figured in conventional manner with a semi-circular annular corrugation, the material for surround 17 being conventional, such as impregated cloth, rubber or syn thetic resin foam. Permanent magnet assembly 19 is fixedly supported by basket ll rearward of voice coil support member 15 and diaphragm 14 in coincident axial alignment therewith. The foregoing described means and arrangement are believed to be conventional.

Lip 16 of basket 11 is impressed with two oppositely facing and concentric beads 25 and 26. Each bead is defined by coincidently concentric crown and recess surfaces having a curvilinear configuration of about I35"; maximum curvature would be about Circular gasket 23 of round annular cross-section is operably disposed intermediate bead 25 and mounting board 12 for providing an air-tight vapor-proof seal therebetween when compressed. Gasket 23 comprises humidity non-sensitive material such as polyvinylchloride or other well-known material having similar properties, and may either be cast in circular gasket form or may be cut to length from extruded material substantially to form a toroid when operably placed. Adjacent fastening clamps 27 are configured with one end extremity 28 curvilinearly concave to fay with the crown of bead 25 and other end extremity 29 perpendicularly depending to stand-off from board 12 approximately the distance of the combined thickness of lip 16 and compressed gasket 23. Slot 31 is provided centrally of clamp 27 for receiving the threaded shank of screw 32 therethrough for anchoring into board 12. When fastening clamps 27 are so anchored by screw 32 end extremity 28 exerts force on the crown of bead 25 directly perpendicular to board I2 and in coincident concentricity to the gasket circle so that deformation of basket 11 by a radially extending force is avoided, and alignment of the speaker components is not affected by mounting of the speaker.

When properly mounted gasket 23 completely separates speaker 9 from direct contact with mounting board 12 and positions the speaker so that surround 17 will at all times be clear of a grill cloth mask on the speaker enclosure. A convenient size for the gasket material may be about one-eighth inch diameter stock, but any other size may be used. Fastening clamps 27 are positioned so that they contact speaker 9 only on the crown of bead 2S and are free of the edge of basket ll.

FIG. 2 shows loudspeaker 9' mounted in an alternative position on mounting board 12. Loudspeaker 9 is positioned adjacent board 12' completely to one side rather than within opening 13' Gasket 23' is disposed within the recess of head 26' in facing adjacency to board 12' and fastening clamps 27 are reversed in position from that shown in FIG. 1 so that they will standoff from the opposite side of board 12' and exert applied force on the opposite face of the board, and will bear on the crown of head 26'. The selection of mounting positions is optional and if desired either of beads 25 or 26 of FIG. 1, or of beads 25' or 26' of FIG. 2 can be eliminated without affecting the substance of this invention. The configuration of beads 25 and 26 may be other than shown such as ridged or channeled and extending circumferentially other than in a circular pattern, and similarly gasket 23 may be of any corresponding toroidal or other configuration, the salient requirement for distortion-free mounting being that the applied and reactive forces exerted by mounting be in coincident relation on the loudspeaker and without ra dial offset. and that the gasket material be substantially unaffected by changes in ambient conditions of humidlty.

FIG. 3 shows in cross-section a peripheral portion of a preferred embodiment of this invention. Loudspeaker 9" comprises basket 11'. diaphragm l4, and surround 17', with lip 16' of basket 11' being configured as a substantially planar rim which is received into slotted gasket 36. The gasket material may be similar to the hereinbefore mentioned, polyvinylchloride of 72 durometer reading being satisfactory. As shown, gasket 36 is of substantially circular transverse annular crosssection with extremities 37 providing a flare for the slot to facilitate easy application of the gasket onto lip 16 of basket 11'. The basket material may conveniently be 18 or 20 gauge sheet metal for speakers having a diam eter up to about eight inches and of heavier gauge for larger sizes. The gasket diameter conveniently may be about 0. l 7 inch for a range of speaker sizes and larger if necessary. An extruded length of gasketing may be cut to length and placed over the lip of a speaker and then be fused at the ends to effect a continuous circular gasket.

Gasket 36 rests on mounting board 12 adjacent opening 13 and is compressed thereon by application of force transmitted by clamps 27. One end extremity 29' bears on mounting board 29 and the other end rests forcibly on gasket 36 with force securing the clamp being exerted by screw 32' anchored in the mounting board.

Surround 17' is configured with the inner peripheral edge 17" cemented to diaphragm l4, and the outer pefipheral edge 17" overlaying and cemented to lip 16' if basket 11', in non-coincident planes with the inner ,ieriphery recessed below the outer periphery, a recessed distance of about 0.14 inch having been found satisfactory for a four and one-half inch diameter speaker to provide needed clearance for diaphragm operation and for rendering the speaker output-to-input power ratio nearly constant, for example, to within four to five descibels decibels constancy for a given input power over a range of from less than cps to 20,000 cps. Lesser or greater planar offset would correspondingly be provided for surrounds of smaller or greater diameter. respectively. To insure fixed placement, gasket 36 may be cemented to lip 16' and to surround edge 17".

Speaker 9 may be mounted on a baffle in either manner as shown in FIGS. 1 and 2 with clamps 27' and screws 32 being appropriately directly or reversely positioned as necessary. Surround 17' is shown with a rearwardly extending corrugation, however, a configuration may be employed in like manner to that shown in FIG. 1.

Constancy of ratio between acoustic output to input power has been found empirically to be enhanced by the frontal extremities of the frame and the diaphragm suspension being disposed forwardly of the diaphragm when at rest at least a distance substantially equal to the amplitude of forward movement of the diaphragm from rest. A flare angle of about 2 degrees from cylindrical in the wall of the surround running from the bottom of the annular corrugation to the frontal plane has been found empirically to be nearly optimum for pro viding the quality of response obtainable from the de scribed speakers, and together with the resilient stressfree mounting described assures stable, distortion-free performance and output.

While positioning fastening screws directly through the rim of the loudspeaker frame and the gasket would serve to avoid imposing bending stress on the frame, the arrangement suffers the obvious disadvantage of piercing the gasket and substantially severing the seal at numerous places and of anchoring screws virtually at the periphery of a speaker opening so that they would tend to split out from the baffle and loosen. To widen the frame lip lessens the integrity of the seal and renders the frame more vulnerable to distortion. reducing the advantages obtained by the foregoing described configuration and mounting employing levered clamps.

I claim:

1. In a loudspeaker embodying means reciprocally driven responsively to signal current biasing, an improvement for rendering more nearly constant the ratio of acoustic output to input power throughout the range of acoustic response. comprising in combination,

a. a structural basket,

b. a voice coil disposed for axial movement within a force field responsively to biasing force created by a signal current in said voice coil,

c. a diaphragm aligned and connected integrally to said voice coil, said diaphragm being recessed rearwardly from the forward extremity of said basket to be drivable not substantially forward thereof,

d. an annular suspension collar fixed at its inner peripheral extremity to the circumferential extremity of said diaphragm and at its outer peripheral extremity to the forward extremity of said basket and configured with an annular corrugation having a minimum depth in the direction of drive ofsaid diaphragm at least substantially as great as the amplitude of such drive from rest,

normal to the plane of such baffle.

2. The apparatus of claim 1 wherein the forward extremity of the basket is receivable in a gasket recess configured as an annular slot extending from the inner periphery of the gasket.

3. The apparatus of claim 1 wherein said fastening means comprise substantially rigid elongated clips levered against anchorable fulcrum posts. 

1. In a loudspeaker embodying means reciprocally driven responsively to signal current biasing, an improvement for rendering more nearly constant the ratio of acoustic output to input power throughout the range of acoustic response, comprising in combination, a. a structural basket, b. a voice coil disposed for axial movement within a force field responsively to biasing force created by a signal current in said voice coil, c. a diaphragm aligned and connected integrally to said voice coil, said diaphragm being recessed rearwardly from the forward extremity of said basket to be drivable not substantially forward thereof, d. an annular suspension collar fixed at its inner peripheral extremity to the circumferential extremity of said diaphragm and at its outer peripheral extremity to the forward extremity of said basket and configured with an annular corrugation having a minimum depth in the direction of drive of said diaphragm at least substantially as great as the amplitude of such drive from rest, e. a moisture non-absorbent gasket disposed for seating the forward extremity of said basket upon a baffle to provide a vapor proof, distortion free mounting therefor, f. fastening means anchorable to a baffle and configured to forcibly compress said gasket and retain said basket immobile upon such baffle wherein contact of said fastening means is made in substantial incidence with the projection of said gasket normal to the plane of such baffle.
 2. The apparatus of claim 1 wherein the forward extremity of the basket is receivable in a gasket recess configured as an annular slot extending from the inner periphery of the gasket.
 3. The apparatus of claim 1 wherein said fastening means comprise substantially rigid elongated clips levered against anchorable fulcrum posts. 